/** 
 * LT, ET mode demo for epoll 
 * @date 2021/7/17
 * @author martin(zhangming163.com)
 */

#include <sys/socket.h>
#include <sys/types.h>
#include <sys/epoll.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <string.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <assert.h>
#include <errno.h>

#define MAX_EVENT_NUMBER      1024
#define BUFFER_SIZE           10

typedef struct sockaddr SA;

/* 将文件描述符设置成非阻塞的 */
int setnonblocking(int fd)
{
    int old_option = fcntl(fd, F_GETFL);
    int new_option = old_option | O_NONBLOCK;
    fcntl(fd, F_SETFL, new_option);
    return old_option;
}

/* 将文件描述符fd上的EPOLLIN注册到epollfd指示的epoll内核事件中，参数enable_et指定是否对fd启用ET mode */
void addfd(int epollfd, int fd, bool enable_et)
{
    struct epoll_event event;
    event.data.fd = fd;
    event.events = EPOLLIN;
    if (enable_et) {
        event.events |= EPOLLET;
    }

    epoll_ctl(epollfd, EPOLL_CTL_ADD, fd, &event);
    setnonblocking(fd);
}

/* LT模式的工作流程 */
void lt(struct epoll_event *events, int number, int epollfd, int listenfd)
{
    char buf[BUFFER_SIZE];
    for (int i = 0; i < number; i++) {
        int sockfd = events[i].data.fd;
        if (sockfd == listenfd) {
            struct sockaddr_in client_address;
            socklen_t client_addrlength = sizeof(client_address);
            int connfd = accept(listenfd, (SA *)&client_address, &client_addrlength);
            addfd(epollfd, connfd, false); /* 对connfd禁用ET mode */
        }
        else if (events[i].events & EPOLLIN) {
            /* 只要socket读缓存中还有未读出的数据，这段代码就被触发 */
            printf("event trigger once\n");
            memset(buf, '\0', BUFFER_SIZE);
            int ret = recv(sockfd, buf, BUFFER_SIZE - 1, 0);
            if (ret <= 0) {
                close(sockfd);
                continue;
            }

            printf("get %d bytes of content: %s\n", ret, buf);
        }
        else {
            printf("something else happend \n");
        }
    
    }
}

/** ET模式的工作流程 */
void et(struct epoll_event* events, int number, int epollfd, int listenfd)
{
    char buf[BUFFER_SIZE];
    for (int i = 0; i < number; i++) {
        int sockfd = events[i].data.fd;
        if (sockfd == listenfd) {
            struct sockaddr_in client_address;
            socklen_t client_addrlength = sizeof(client_address);
            int connfd = accept(listenfd, (SA *)&client_address, &client_addrlength);

            addfd(epollfd, connfd, true); /* 对connfd开启ET mode */
        }
        else if (events[i].events & EPOLLIN) {
            /* 这段代码不会被重复触发，所以我们循环读取数据，以确保把socket读缓存中的所有数据读出 */
            printf("event trigger once\n");

            while (1) {
                memset(buf, '\0', BUFFER_SIZE);
                int ret = recv(sockfd, buf, BUFFER_SIZE - 1, 0);
                if (ret < 0) {
                    /* 对于非阻塞IO，下面的条件成立表示数据已经全部读取完毕。
                    此后，epoll就拿再次触发sockfd上的EPOLLIN事件，以驱动下一次读操作 */
                    if ((errno == EAGAIN) || (errno == EWOULDBLOCK)) {
                        printf("read later\n");
                        break;
                    }
                    close(sockfd);
                    break;
                }
                else if (ret == 0) {
                    close(sockfd);
                }
                else {
                    printf("get %d bytes of content: %s\n", ret, buf);
                }
            }
        }
        else {
            printf("something else happed \n");
        }
    }
}


/* epoll的LT, ET mode工作模式区别示例 */
int main(int argc, char *argv[])
{
    if (argc <= 2) {
        printf("usage: %s ip_address port_number\n", argv[0]);
        return 1;
    } 

    const char *ip = argv[1];
    int port = atoi(argv[2]);

    int ret = 0;
    struct sockaddr_in address;
    bzero(&address, sizeof(address));
    address.sin_family = AF_INET;
    inet_pton(AF_INET, ip, &address.sin_addr);
    address.sin_port = htons(port);

    int listenfd = socket(AF_INET, SOCK_STREAM, 0);
    assert(listenfd >= 0);

    ret = bind(listenfd, (SA *)&address, sizeof(address));
    assert(ret != -1);

    ret = listen(listenfd, 5);
    assert(ret != -1);

    struct epoll_event events[MAX_EVENT_NUMBER];
    int epollfd = epoll_create(5);
    assert(epollfd != -1);
    addfd(epollfd, listenfd, true);

    while (1) {
        int ret = epoll_wait(epollfd, events, MAX_EVENT_NUMBER, -1);
        if (ret < 0) {
            printf("epoll failure\n");
            break;
        }

        lt(events, ret, epollfd, listenfd); /* LT mode */
        // et(events, ret, epollfd, listenfd); /* ET mode */

    }
    
    close(listenfd);
    return 0;
}
